USMLE Step 1 Question 295

Question:

A 58-year-old alcoholic man presents with diarrhea for 4 days duration. He further explains that for the past week he has been taking “heartburn medication” for worsening epigastric pain. Blood pressure was 100/60 with a pulse rate of 95 bpm. Laboratory studies were all normal except serum potassium of 3.3mEq/L. Which of the following medications did the patient most likely overuse?

Correct Answer: D.  Magnesium Hydroxide

Alcoholics commonly have gastritis for which they seek relief with over-the-counter medications such as antacids. There are various antacids in the answer choices, each with their own side-effect profile. Magnesium hydroxide (choice D) is the only medication listed that has an overuse effect of diarrhea and hypotension. Additional side-effects include hyporeflexia, hypokalemia, and cardiac arrest.

Cimetidine (choice A) is a H2 receptor blocker with side effects of gynecomastia, impotence, dizziness, and headaches.

Aluminum hydroxide (choice B) is an antacid with side effects of constipation, hypophosphatemia, proximal muscle weakness, osteodystrophy, seizures, and hypokalemia.

Calcium carbonate (choice C) is an antacid with side effects of hypercalcemia, rebound acid secretion, and hypokalemia.

Ondansetron (choice E) is a centrally acting anti-emetic selectively antagonizing 5-HT3 receptors. Side effects include headache and constipation.